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wtf_nature
Great Strobing Eyestalks!
Flatworms have no body cavity other than the gut (and the smallest free-living forms may even lack that!) and lack an anus; the same hole both takes in food and expels waste. Because they don't have any other cavity they have to be flat, or parts of them will suffocate or starve - there's simply nothing to make a circulatory system out of.
Flatworms used to be divided into three groups. The mostly free-living Turbellaria; The Trematoda, or flukes, all parasitic; and the Cestoda, or tapeworms. Recent DNA studies are complicating things.
The turbellarians are interesting enough, and often very pretty, and some indulge in penis-fencing and guard their young - the simplest animals to do so.
But of course I'm not going to be talking about anything as inoffensive as turbellarians.
The parasitic flatworms can enjoy life cycles, and anatomies, just as complicated as anything else in the parasitic world. They can be extremely fussy, as well, living only in the bladders of a particular species of desert frog, for example, or living only in one small section of your intestine and viciously suppressing anything else that tries to set up shop there. They can navigate inside your body, boring out thru your stomach lining and cruising happily along the inner surface of your abdominal cavity until they reach your liver. Others just stay in your arteries, cruising round and round and popping out babies. The Schistosoma blood flukes mate for life, whilst thus cruising (There's even gay blood flukes just as devoted to each other). Others can can be up to 20 metres long. Yes, 20 METRES. Admittedly not in humans. In humans the record is just under 9 metres, and makes a nice display in the Meguro Parasitiological Museum in Tokyo, which I heartily recommend. They have a dressing-gown strap nailed up next to it, so you can compare sizes.
They've also been around a very long time indeed. They've survived mass extinctions, lingering around to transfer their attentions to new dominant clades as they arise. Even the ones that are specific to humans are most closely related to the ones that cycle between wild ungulates and the big cats. They've been with us since we were ape-men, scavenging meals from lions
Then, of course, there's everybody's favorite fluke - Leucochloridium paradoxum, the White-Green Paradox, because tetrabinary insisted on a more informative repost :D
The larval stages of Leuco p. develop inside apple snails. They need to get into the adult host, a bird.
This shouldn't be a problem, I'm imagining you thinking - prey species to predator species, parasite going along for the ride. Parasites of insects becoming parasites of insectivores, or vice versa, is quite common. There's plenty of insect-eating birds, too - such as tits. On the other hand, insects are small and lack the body mass to support a really healthy load of parasite eggs. A snail is nice and big, but there aren't many snail-eating birds, such as thrushes.
But Leucochloridium isn't waiting for a snail-eating bird, it's waiting for an insectivore.
So how does a parasitic fluke in a snail's digestive gland get from snail to tit?
By turning the snail into a caterpillar. Or at least, by sticking green-and-white-banded cercariae-stuffed sporocyst tubes up the unfortunate snail's eyestalks (the left, for preference), inflating them until the snail can't retract it's eyes, and pulsing away.
As you can imagine something oozing thru the leaf-litter with strobing eyestalks is incredibly conspicuous. Soon, the snail, already half out its mind from the influence of the parasite shoving whacking great pulsing ovaries up its eyestalk, is minus half it's head, and the bird has a gutfull of merry little cercariae, invading its intestines. Later on, the adults will breed, and the eggs will end up in some unlucky snail's meal of fresh bird poo.
Video of one with a sporocyst tube up each eyestalk, and info here
also
and this one, who apparently gave up trying to push it's tubes all the way a little snails undersized eyestalks.
It's even more effective if you imagine sound-effects - a nice "WhuuumWhuummmWhummm" perhaps
I showed this video to my wife. She says it looks like a porno. Martian porno, perhaps
Flatworms used to be divided into three groups. The mostly free-living Turbellaria; The Trematoda, or flukes, all parasitic; and the Cestoda, or tapeworms. Recent DNA studies are complicating things.
The turbellarians are interesting enough, and often very pretty, and some indulge in penis-fencing and guard their young - the simplest animals to do so.
But of course I'm not going to be talking about anything as inoffensive as turbellarians.
The parasitic flatworms can enjoy life cycles, and anatomies, just as complicated as anything else in the parasitic world. They can be extremely fussy, as well, living only in the bladders of a particular species of desert frog, for example, or living only in one small section of your intestine and viciously suppressing anything else that tries to set up shop there. They can navigate inside your body, boring out thru your stomach lining and cruising happily along the inner surface of your abdominal cavity until they reach your liver. Others just stay in your arteries, cruising round and round and popping out babies. The Schistosoma blood flukes mate for life, whilst thus cruising (There's even gay blood flukes just as devoted to each other). Others can can be up to 20 metres long. Yes, 20 METRES. Admittedly not in humans. In humans the record is just under 9 metres, and makes a nice display in the Meguro Parasitiological Museum in Tokyo, which I heartily recommend. They have a dressing-gown strap nailed up next to it, so you can compare sizes.
They've also been around a very long time indeed. They've survived mass extinctions, lingering around to transfer their attentions to new dominant clades as they arise. Even the ones that are specific to humans are most closely related to the ones that cycle between wild ungulates and the big cats. They've been with us since we were ape-men, scavenging meals from lions
Then, of course, there's everybody's favorite fluke - Leucochloridium paradoxum, the White-Green Paradox, because tetrabinary insisted on a more informative repost :D
The larval stages of Leuco p. develop inside apple snails. They need to get into the adult host, a bird.
This shouldn't be a problem, I'm imagining you thinking - prey species to predator species, parasite going along for the ride. Parasites of insects becoming parasites of insectivores, or vice versa, is quite common. There's plenty of insect-eating birds, too - such as tits. On the other hand, insects are small and lack the body mass to support a really healthy load of parasite eggs. A snail is nice and big, but there aren't many snail-eating birds, such as thrushes.
But Leucochloridium isn't waiting for a snail-eating bird, it's waiting for an insectivore.
So how does a parasitic fluke in a snail's digestive gland get from snail to tit?
By turning the snail into a caterpillar. Or at least, by sticking green-and-white-banded cercariae-stuffed sporocyst tubes up the unfortunate snail's eyestalks (the left, for preference), inflating them until the snail can't retract it's eyes, and pulsing away.
As you can imagine something oozing thru the leaf-litter with strobing eyestalks is incredibly conspicuous. Soon, the snail, already half out its mind from the influence of the parasite shoving whacking great pulsing ovaries up its eyestalk, is minus half it's head, and the bird has a gutfull of merry little cercariae, invading its intestines. Later on, the adults will breed, and the eggs will end up in some unlucky snail's meal of fresh bird poo.
Video of one with a sporocyst tube up each eyestalk, and info here
also
Click to viewand this one, who apparently gave up trying to push it's tubes all the way a little snails undersized eyestalks.
It's even more effective if you imagine sound-effects - a nice "WhuuumWhuummmWhummm" perhaps
I showed this video to my wife. She says it looks like a porno. Martian porno, perhaps